1. Field Of The Invention
The apparatus of the present invention relates to downhole valves. More particularly, the present invention relates to a disc valve, constructed of a breakable material, such as glass, positioned in the flowbore of a tubing string that prevents flow of fluid through the bore from either direction. When flow is desired, the breakable disc is ruptured, and the flow is allowed to commence within the bore. In an additional embodiment, the disc valve assembly would be sheared free from the wash pipe and pushed to a position below the telltale screen so that the opening for production would be substantially larger than with the first embodiment.
2. General Background
In the general process for drilling and production of oil and gas wells, at that point in the process where a hydrocarbon formation has been located at a particular depth, normally an exterior casing would be lowered down the borehole through the area of production, known as the production zone. The exterior casing is perforated with the use of a perforating gun or the like. Using electric wireline and setting tools, or some other means, a permanent type packer, referred to as a "sump packer" is usually set below the perforations. Subsequently, an internal tubing string, together with sand screen and blank pipe, packer and packer extension, hydraulic setting tool, cross-over tool, and wash pipe, are positioned within the exterior casing to engage with the "sump packer". The annulus between the sand screen and the exterior perforated casing is packed off, utilizing certain procedures. This packing off is necessary so that the interior tubing would be utilized to carry the recovered hydrocarbons to the surface. The area around the perforations is prepared, so that the flow of hydrocarbons may commence.
For example, the well must be gravel packed, so that the flow of sand or the like out of the formation is prevented during recovery of the hydrocarbons. The present invention would be utilized following the gravel packing procedure, with the assignee company, Completion Services, Inc., would designate as the "Complete Gravel Pack," which would include a hydraulic setting tool and crossover being run into the well with the required sandscreen and blank pipe. The packer assembly would be seated using pump pressure applied to the tubing. After it is seated, the crossover valve may be opened and closed. With the crossover valve closed, the packer may be pressure tested by pumping down the casing. Fluid may be pumped into the formation to establish injection rate. Also, the formation may be acidized, if necessary. With the crossover valve open, sand slurry may be circulated to place sand outside of the screen and into the formation until adequate gravel pack is obtained. After removal of the setting tool and crossover, a production seal assembly is run in for production of the zone.
After gravel packing is complete, oftentimes the well may not necessarily be pressure balanced. The formation, under these conditions, may tend to absorb the well fluid into the production zone or the fluid in the zone may tend to flow into the well. In either case, this could lead to unacceptable (a) loss of expensive well fluid, (b) damage to the formation, (c) danger of a potential well blow-out or co-mingling of formation fluids. In the present state of the art, if there can be a prediction in which direction the pressure differential will exist within the well, a flapper valve can be utilized which would hold pressure in one direction only. However, flapper valves can be easily damaged, activated premature, leak or rupture at too low a pressure differential. Therefore, there is a need in the art for a valve which would prevent the movement of fluids within the well bore in either direction, and under varying degrees of pressure differential within the well.
There have been patents issued in the art which relate to valves in operation downhole, during the recovery of hydrocarbons during production, etc., the most pertinent being as follows:
______________________________________ ISSUE PATENT NO. TITLE DATE ______________________________________ 4,658,902 "Surging Fluids Downhole In Apr. 21, 1987 An Earth Borehole" 4,651,827 "Hydraulically Controlled Mar. 24, 1987 Safety Valves For Incorporation In Production Tubes Of Hydrocarbon Production Wells" 4,691,775 "Isolation Valve With Frangible Sep. 8, 1987 Flapper Element" 3,831,680 "Pressure Responsive Auxiliary Aug. 27, 1974 Disc Valve And The Like For Well Cleaning, Testing And Other Operations" 3,599,713 "Method And Apparatus For Aug. 17, 1971 Controlling The Filling Of Drill Pipe Or The Like With Mud During Lowering Thereof" 3,024,846 "Dual Completion Packer Tool" Nov. 15, 1957 2,855,943 "Circulation Port Assemblies Oct. 14, 1958 For Tubing Or Well Pipe" 2,626,177 "Tool For Hydraulically Jan. 20, 1953 Displacing Well Materials" 2,565,731 "Disk Perforator For Pipes Aug. 28, 1951 In Wells" 2,545,504 "Completion Shoe" Mar. 20, 1951 ______________________________________
Other objects of the invention will be obvious to those skilled in the art from the following description of the invention.